Technical Field
The present disclosure relates to a photographing lens module. More particularly, the present disclosure relates to a photographing lens module which is applicable to portable electronic devices.
Description of Related Art
Due to the popularity of personal electronic products and mobile communication products having camera functionalities, such as smart phones and tablet personal computers, the demand for compact photographing lens modules has been increasing and the requirements for high resolution and image quality of present compact photographing lens modules increase significantly.
A plastic lens element is generally used to effectively reduce the manufacturing cost of the photographing lens module. A conventional plastic lens element is typically formed by an injection molding method and has a smooth and bright surface, which is featured with high reflectivity. Accordingly, when the non-imaging light is reflected from the surfaces of other optical elements of the photographing lens module to the surface of the plastic lens element, the non-imaging light reflected from the surface of the plastic lens element cannot be effectively attenuated and would be incident on the surfaces of lens elements of the photographing lens module.
For suppressing the non-imaging light of the photographing lens modules, one of the conventional methods is applying ink on the lens elements. That is placing a lens element on a turntable, applying the ink on the edge of the lens element by a brush and drying the ink by air or heating. However, the method could not be applied in the plastic lens elements with compact sizes and high accuracy due to the variation of ink applying exceeds the scale of the plastic lens elements. On the other hand, removing the excess ink by wiping is also difficult for the plastic lens elements. To solve the problem, the technology of the optical refractive index matching layer configured in a gap between the black barrel and the lens element has been developed in order to reduce the reflection in the edge of the lens element, but there are many limitations to configure the optical refractive index matching layer.
Given the above, a surface property of the plastic lens element relates to the image quality of the photographing lens module. How to reduce the non-imaging light reflected from the surface of the plastic lens element has become one of the important subjects, so that the image quality of the compact photographing lens modules can be enhanced, and the requirements of high-end optical systems with camera functionalities can be satisfied.